locale.c: Fix compilation error on some platforms

Commit 73d66f354cd4df0324b11e46af48f66bd5c1dd15 introduced a compilation
error into some platforms lacking nl_langinfo(3)  (generally Windows,
but their compiler is more lenient in this regard.

Simply add a 'const' to the declaration to fix it.

1 files changed, 1 insertions, 1 deletions

diff --git a/locale.c b/locale.c
index 8b5c5aeaf8..3735726ac6 100644
--- a/locale.c
+++ b/locale.c
@@ -4467,7 +4467,7 @@ S_my_langinfo_i(pTHX_
         retval++;
 
         /* And stop before any '@' */
-        char * modifier = strchr(retval, '@');
+        const char * modifier = strchr(retval, '@');
         if (modifier) {
             char * code_set_name;
             const Size_t name_len = modifier - retval;